In general, a pneumatic radial tire is framed by a carcass extending toroidally between a pair of bead portions and belt layers composed of rubberized steel cords are disposed as reinforcing layers on an outside of the carcass in a radial direction of the tire. The steel cords used for such belt layers have been studied variously since the past from aspects of improving steering stability and riding comfortability.
For example, Patent Literature 1 describes a technology for improving steerage, stability and others during cornering by using specific steel cords of thin wires (diameter of the wire: 0.06 to 0.10 mm). Patent Literature 2 discloses a tire specifying steel cords by bending resistance and tensile elongation and Patent Literatures 3 to 5 disclose a tire specifying a belt layer by a relational expression of a diameter of the cord, a number of filaments within one cord and a number of driven cords of the belt layer, respectively.
Furthermore, Patent Literature 6 discloses a tire having steel cords composed of predetermined steel filaments and specifying a predetermined range of values defined by belt bending rigidity, strength of the cord and an amount of voids of the belt cords and Patent Literatures 7 through 9 disclose tire reinforcing steel cords having a predetermined strand structure and specifying a predetermined range of values defined by strength of the cord, elongation when the cord ruptures and cord bending rigidity. Still more, Patent Literature 10 discloses a tire specifying a belt by a belt cord strand structure, a diameter of wire and a number of driven belt cords, Patent Literature 11 discloses a tire that meets predetermined requirements in terms of a strand structure, bending strength/cord strength ratio, strength of cord and a diameter of wire and Patent Literature 12 discloses a tire in which a belt ply specifying a belt cord structure and a number of driven cords is disposed through an intermediary of cushion rubber, respectively.    Patent Literature 1: Japanese Patent Application Laid-open No. Sho.59-38102 Gazette (Claims and others)    Patent Literature 2: Japanese Patent Application Laid-open No. Sho.60-185602 Gazette (Claims and others)    Patent Literature 3: Japanese Patent Application Laid-open No. Sho.63-2702 Gazette (Claims and others)    Patent Literature 4: Japanese Patent Application Laid-open No. Sho.63-2703 Gazette (Claims and others)    Patent Literature 5: Japanese Patent Application Laid-open No. Sho.63-2704 Gazette (Claims and others)    Patent Literature 6: Japanese Patent Application Laid-open No. Sho.64-85381 Gazette (Claims and others)    Patent Literature 7: Japanese Patent Application Laid-open No. Sho.64-85382 Gazette (Claims and others)    Patent Literature 8: Japanese Patent Application Laid-open No. Sho.64-85383 Gazette (Claims and others)    Patent Literature 9: Japanese Patent Application Laid-open No. Sho.64-85384 Gazette (Claims and others)    Patent Literature 10: Japanese Patent Application Laid-open No. Hei.1-141103 Gazette (Claims and others)    Patent Literature 11: Japanese Patent Application Laid-open No. Hei.3-74206 Gazette (Claims and others)    Patent Literature 12: Japanese Patent Application Laid-open No. Hei.3-143703 Gazette (Claims and others)